The present invention generally relates to a stacked-chip semiconductor device in which a plurality of semiconductor chips having different functions are stacked in a three-dimensional direction, and a manufacturing method thereof. More particularly, the present invention relates to a stacked-chip semiconductor device adapted for improved transmission speed of electric signals, and a manufacturing method thereof.
Recently, a stacked-chip semiconductor device is developed in which a plurality of semiconductor chips having different functions are stacked on a single circuit board (carrier substrate) in a single package.
Hereinafter, a semiconductor device having three semiconductor chips stacked on a circuit board will be described as a typical example of such a conventional stacked-chip semiconductor device.
FIG. 10 is a cross-sectional view showing the structure of a conventional stacked-chip semiconductor device.
Referring to FIG. 10, the conventional semiconductor device includes a circuit board 3, a first semiconductor chip 7, a second semiconductor chip 8, and a third semiconductor chip 10. The circuit board 3 has wiring electrodes 1 on its top surface and terminal electrodes 2 on its bottom surface. The first semiconductor chip 7 is bonded to the circuit board 3 with face-up state and has first electrodes 4, second electrodes 5 and third electrodes 6 at its surface. The second semiconductor chip 8 is flip-chip connected to the surface of the first semiconductor chip 7 with face-down state, and is electrically connected to the first electrodes 4 of the first semiconductor chip 7. The third semiconductor chip 10 is bonded to the rear surface of the second semiconductor chip 8 with face-up state and has fourth electrodes 9 at its surface. The second electrodes 5 of the first semiconductor chip 7 and the fourth electrodes 9 of the third semiconductor chip 10 are electrically connected to each other by first thin metal wires 11. The wiring electrodes 1 of the circuit board 3 and the third electrodes 6 of the first semiconductor chip 7 are electrically connected to each other by second thin metal wires 12. The top surface region of the circuit board 3 including the semiconductor chips and the thin metal wires is sealed with an insulating resin package 13. Note that the gap between the first and second semiconductor chips 7, 8 is sealed with a resin that is different from the resin package 13.
In the conventional semiconductor device of FIG. 10, a plurality of types of semiconductor chips that will serve as memory elements, logic elements and the like are mounted on the circuit board 3. This enables implementation of a multi-functional semiconductor device capable of implementing multifunctional elements in a single package.
In this conventional semiconductor device, however, thin metal wires are used as means for electrically connecting the chips other than the flip-chip-connected semiconductor chips. This puts limitations on improvement in transmission speed of electric signals. In other words, the use of the electric connection means like thin metal wires in a multi-functional semiconductor device having multiple chips (two or more chips) stacked in a single package results in a reduced signal propagation speed between the chips. Therefore, such a conventional semiconductor device cannot meet future expectation of improved operation speed of the semiconductor device. In other words, there is a need for an improved signal speed of a semiconductor device having two or more chips, e.g., three chips, stacked in a single package.